X-Git-Url: http://git.cascardo.info/?a=blobdiff_plain;f=Documentation%2FDMA-attributes.txt;h=98bf7ac29aad8fff65e88bc6b1e6c2a6fc3a5033;hb=a4256bc9ec36159e84d710c7c44aaa244a6380a8;hp=2d455a5cf6718639062e237ff859fc045d7f4911;hpb=3bc42f3f0ef13a8239138a4c00a0b782f029f23d;p=cascardo%2Flinux.git

diff --git a/Documentation/DMA-attributes.txt b/Documentation/DMA-attributes.txt
index 2d455a5cf671..98bf7ac29aad 100644
--- a/Documentation/DMA-attributes.txt
+++ b/Documentation/DMA-attributes.txt
@@ -126,3 +126,20 @@ means that we won't try quite as hard to get them.
 
 NOTE: At the moment DMA_ATTR_ALLOC_SINGLE_PAGES is only implemented on ARM,
 though ARM64 patches will likely be posted soon.
+
+DMA_ATTR_NO_WARN
+----------------
+
+This tells the DMA-mapping subsystem to suppress allocation failure reports
+(similarly to __GFP_NOWARN).
+
+On some architectures allocation failures are reported with error messages
+to the system logs.  Although this can help to identify and debug problems,
+drivers which handle failures (eg, retry later) have no problems with them,
+and can actually flood the system logs with error messages that aren't any
+problem at all, depending on the implementation of the retry mechanism.
+
+So, this provides a way for drivers to avoid those error messages on calls
+where allocation failures are not a problem, and shouldn't bother the logs.
+
+NOTE: At the moment DMA_ATTR_NO_WARN is only implemented on PowerPC.